Lisa, an experienced shipping clerk can fill an order in 9 hours. Felipe a clerk needs 11 hours to do the same job. Working together how long will it take them to fill the order.
Lisa =L
Felipe =F
1/L + 1/F =1 / T
1/9 +1/11 =20/99
T = 99 / 20 = 4.95 hours to finish the order when working together.
